Lifting jack



Sept. 10, 1957.

Filed Dec. 2. 1955 R. R. DALY 2,805,581

LIFTING JACK 2 Sheets-Sheet 1 I 44 O a6 76 g I I 1 MENTOR v Roberf 3,1761

- ATTORNEYS Sept. 10, 1957 Filed Dec. 2, 1955 2 Sheets-Sheet 2 5 a m 1 9 18 a 22 12 6v 3 W E 10 I g 14L E .30 g X 6 60 a2 g g g 76 INVENTOR.' Robe/"2* R..Da{y

ATTORNEYS,

United States Patent M LIFTIN G JACK Robert R. Daly, Hopkins, Minn., assignor to Pneumatic Jacks, Inc., St. Paul, Minn., a corporation of Minnesota Application December 2, 1955, Serial No. 550,655

4 Claims. (Cl. 74144) This invention relates to improvements in'a lifting jack. In general, the jack to which the present improvement pertains is used to elevate forms and scaffolding in connection with the erection of molded concrete buildings wherein a multiplicity of jacks are used to support the scalfolding, and each jack is arranged with gripping bits to ride or crawl upwardly upon individual jack rods that extend vertically from the concrete walls being formed. More particularly, the invention is concerned with improvements in the construction and arrangement of the dogs or bits that engage the jack rod and actually support the scafifolding and forms.

Lifting jacks for elevating forms and scaffolding in the erection of concrete buildings are known in the art and are exemplified in Patents 2,673,064; 2,673,065; and 2,673,- 066, all of which are assigned to the present assignee. As disclosed in the foregoing patents, the jack consists of a pair of relatively movable members that encompass a jack rod and form an expansible chamber that is situated beneath a supporting form and on actuation elevate the form and scaffolding at periodic intervals to permit construction of the building walls in a continuous operation. Each of the relatively movable members of the jack carries a set of sharpened bits that bite into or grip the jack rod to support the load on the rod. The operation of the two parts are intermittent so that during relative movement of one of the parts, the other must support the load on the jack rod by means of the sharpened bits. These .sets of bits are composed of very hard steel that have been initially sharpened to a cutting edge, and to enable them to grip the rod and also move relative to the rod, they are angularly disposed with the rod and biased towards the rod so that the dragging movement of the bits against the rod and the intermittent action of the bits tends to dull the sharpened edges. This constituted a serious problem with prior bits, because dull bits will not properly grip the jack rod and frequently cause backsliding of the jack and a consequent tilting of the molding form which, in turn, throws the jack out of alignment with the jack rod. A review of the patents mentioned heretofore as well as another related Patent 2,673,067, also assigned to the present assignee, reveals that the problem is a serious one and that numerous efiorts have been made to correct it.

Because the prior bits were each provided with only one sharpened edge, a complete bit replacement was necessary each time the sharpened edge was dulled, and as sharpening tends to reduce the length of the prior bits, replacement was time consuming and costly and frequently resulted in variations in the biasing effect against the jack rod, thereby tending to reduce the efficiency of the jacks, and the consequent retarding of the building operation.

In the present invention, I have provided an improved jack in which each bit is provided with a multiplicity of independent sharpened edges in place of the single sharpened edge found in the prior arrangements, together with an improved arrangement of the bits so as to make them more effective. The bits forming the present invention Patented Sept. 10, 1957 ened edge and thereafter the bit may be reversed in the holder to provide four or more additional sharpened edges, thereby greatly increasing the life of each bit before resharpening or replacement. Additionally, in the present invention, the tension of each set of bits is provided through the spring biasing of a pressure plate working against all of the bits of a set which tends to equalize the pressure, and if any one bit is not in proper alignment with the jack rod, provision is made for individual adjustment of the tension thereof.

An object of the invention is to provide in conjunction with a jack rod, and a lifting jack, gripping bits that engage the rod provided with a multiplicity of interchangeable gripping surfaces.

Another object is to provide in combination with a climbing jack, rod engaging bits that are of linear configuration and are multi-sided forming a multiplicity of individual edges at each end of the bit, and in which each edge is or may be sharpened to provide a mutiplicity of individual biting edges each of which is capable of engaging a jack rod, together with suitable meansfor securing the bits to the jack.

A further object is to provide in combination with a lifting jack including a multiplicity of sharpened bits that engage a jack rod, a pressure plate that forms a partial support for the bits, and individually adjustable springs that bias the pressure plate and provide individual adjustment of the bits so that each bit may be made to share an equal portion of the weight of the jack and the load on the jack rod.

Other and further objects may become apparent from the following specification and claims, and in the amended drawings in which:

Fig. l is a bottom plan view of the lifting jack embodying the present invention;

Fig. 2 is a side elevation taken on the line 2-2 of Fig. 1; and

Fig. 3 is an enlarged detail showing of an individual bit holder and bit shown in Figs. 1 and 2.

Referring now to the several figures of the drawing, the invention will be described in detail. General reference numeral 5 indicates a lifting jack that is adapted to engage a load on its upper surface, seen in Fig. 2, and to elevate the same with respect to a jack rod indicated at 6. An upper plate 8 which supports the load and is circular in configuration, is provided with an annular depending flange 10. The inner surface of the plate 8 is machined within the confines of the flange 10 and forms the upper limits of a chamber indicated at 12. An annular bearing 14 is formed integral with the center of plate 8 and is adapted to embrace the jack rod 6 to hold plate 8 in alignment with the jack rod. A boss 16 is formed on plate 8 and is provided with a threaded opening 18 for admitting fluid under pressure, such as compressed air, to the interior of chamber 12.

An inner plate or piston 20 which is also annular in configuration fits within the interior of plate 8 to form the lower surface of chamber 12. Plate 20 carries on its upper surface an annular diaphragm 22 composed of rubber or similar flexible material that forms a seal on the bottom of chamber 12 as seen in Figs. 1 and 2. Three rods designated by reference character 23 are threadedly secured in spaced relation to each other within the flange 10 and depend from said flange. A tubular bushing 24 surrounds each rod 23, and surrounding each of the bushings is a coil spring 26. The upper ends of the coil springs 26 each engage an ear 28 that protrudes from the lower plate 20 and extends into a cavity 30 in flange 10.

. 3 During relative movements of the plates 8 and 20, they are each supported on jack rod 6. The structure for supporting plate 20 will now be explained. On the lower surface of plate 20 is an annular flange 32, and within this flange, asbest senin Fig. 2, is a tripod consisting of leg portions 3:4,36and 38, each of which has depending spaced arms 40 and 42. ,A bit holder indicated by reference character 44 in Fig. 3 is embedded between the arms 40 and 42 and secured therein by a cotter key 46. It will be apparent from Fig. 2 that three such holders are provided.

Each of the holders 44, as seen in Fig. 3 are pro vided with a hollow rectangular opening 46 within which is mounted a bit 48 that is rectangular in configuration and is also rectangular in cross section. Each of the eightend edges of each bit has'been honed or sharpened as, indicated at 50. The holder44 is provided with a threaded opening 52 adapted to receive a set screw 54 that rigidly holds the bit 48 within the cavity 46. Each of theholders 44 is also provided with a lip structure 56.

Although the bits 48 are disclosed as being rectangular in cross section, it is within the scope of the present invention to form the bits from multi-sided material and therefore the bits could be composed of metal'which is hexagonal or octagonal in cross section. In fact an octagonal bit in the same dimensions as bits 48 could be used in the present form of bitholder without modification of the holder.

Surrounding jack rod 6 and having the configuration of a cloverleaf is a pressure plate 58 that engageseach of the lips 56 of the three holders 44. The pressure plate 58 is held on the under surface of plate 20 by a plurality of threaded rods 60 that extend into plate 20 and are surrounded by coil springs 62 that engage the plate 58and whose tension is regulated by manually adjustable bolts here shown as wing nuts 64.

The upper plate 8 is also supported on the jack rod by a structure which will now be described. Three legs de'signatedin Fig. l as 66, 68. and 70 are secured in bosses 72 of the annular flange 10 by means of cotter keys 74. Secured to the lower ends of the legs 66, 68 and 70 by the bolts 77 is a tripod base 76. On the lower faceof the tripod'76 asseen in Fig.1 are pairs of depending arms 78, 80, and between each of said pair of 'arm'sisa second set of bit holders 44, which are identical in construction with the bitholders. previously described. A second pressure plate 58 embraces the jack rod 6 and engages the lips .56 of the second set of bit holders, A second set of threaded rods '60 that are secured in tripod 76 carries springs 62 and wing nuts 64, and are similar in all details to the construction previ ously described in connection with the bits for plate20.

The operation ofthe invention will now be explained. As 1 disclosed in the previously mentioned patents and particularly Patent 2,673,064, a multiplicity. of jacks are used to support and raise forms andscaifolding used in the construction ofa concrete building, and all of the jacks are connected to a pneumatic system for supplying compressed air for the operation of the jacks. The actual weight or mass to be elevated is resting on the upper surface of plate 8 of each jack. Whenair under pressure is introduced through the threaded opening 18 into chamber 12, the upper set of bits supported on plate 20 grip the jackrod 6 to support the load, and plate 8 moves upwardly compressing the springs 26 until no further movement is allowed by reason of the bushings 24 on the rods 23 engaging the ears 28 on the lower plate 20. Thereafter, and through means not shown the compressed air is vented to atmosphere, and escapes from chamber 12 through the threaded opening 18 in the same manner as it entered the chamber. As chamber 12 is freed from the pressurized fluid, plate 20 and its connected bits are moved upwardly in a followup action caused by the several coil springs 26 surrounding the rods 23 and the lower set of bits bite into the jack rod 6 to assume the weight of the load. Each of the bits 48* is provided with four sharpened edges on each end, and as clearly seen in Fig. 2 only one edge of each bit engages the jack rod at any time to form the holding or gripping surface. As the respective plates are moved upwardly on the jack rods, these sharpened edges tend to become dulled and require'replacement. By removal of the set screw 54, each individual bit may be removed from the respective holder 44 and rotated a quarter turn to provide a new sharpened edge 50, and when all of the edges on one end of a bit are dulled, the bit may be reversed in position to provide four additional sharpened edges on the other end thereof. Frequently in operation, and possibly caused by slight misalignment of the jack rod 6, all ofthe bits may not engage the jack rod with equal tension and this tends to reduce the efi'iciency of the jack. The tension of any one bit may be adjusted by means of the wing nuts 64 operating on the threaded rods 60. v The tension is adjusted against the cloverleaf shapedpressure plate 58 which in turn acts against the lips 56 of the three holders 44. When needed, anyone of the adjusting means may be varied so that all of'the bits will grip ;the jack rod, thus overcoming variations in the jack rod.

The advantages of theprcsent invention reside in the provision of gripping bits, each of which have a multiplicity of sharpened edges that facilitate replacement of sharpened edges without the necessity of physically replacing bits and thereby assures provision for a continuitysof sharpened bits without the necessity of actually replacing bits. Also, both sets of bits are of the same dimension and may be used interchangeably with the upper or lower plates of the jack. A further advantage resides in the provision of the floating pressure plate which distributes pressure on all of the bits and may be adjusted was to assure a uniform gripping of the jack rod by all of the bits forming a set thereof.

While the bits and the adjustment thereof have been disclosed in conjunction with a specific form of jack wherein both sets of bits are carried by the jack beneath the'load, it, will be appreciated that bits of this type may be used in other types of jacks that act in cooperation with a'jackrod and therefore the invention is not limited to the specific jack, but is defined in the terms of the appended claims.

I claim:

l. Ina lifting jack embodying a member that is adapted for relative movement with respect to a jack rod, the improvement consisting of a bit carried adjacent its inner end by said member and formed with a multiplicity of equilateral plane side surfaces and also of substantially greater length than its cross dimension, said bit formed with a transverse outer end surface that extends at right angles with each of saidplane side surfaces to thereby form a multiplicity of sharp biting surfaces on the outer end of the bit for engaging the jack rod, each of said bitingsurfaces forming a separate substitute surface for connecting and supporting 'said member on the jack rod.

'2. In a lifting jack embodying a member that is adapted for relative movement with respect to a jack rod, the improvement consisting of abit carried adjacent its inner end by said member which is square in cross section forming four 'plane side surfaces on the bit, said bit also being of substantially greater length than its cross dimension, said bit formed with a' transverse outer end surface that extends at right angles witheach of said plane side surfaces to thereby form fou'r'sharp biting surfaces on the outer end of the bit for'engaging the jack rod, each of said biting surfacesfo'rming a separate substitute surface for connecting and supporting said member on the jack ro'd.

3. Ina lifting jack embodying a member that is adapted for relative movement with respect to a jack rod, a bit formcdwith a multiplicity of equilateral plane side surfaces and also of substantially greaterlength than its cross dimension, said bit formed with a transverse end surface on each longitudinal end thereof that extends at right angles with each of said plane side surfaces to thereby form a multiplicity of sharp biting surfaces on the opposite ends of the bit for engaging the jack rod, and a bit holder pivotally supported at one end by said member and formed with a hollow socket at its other end which accommodates the lateral dimensions of the bit for receiving and supporting said bit on said member in such a manner as to engage the jack rod.

4. In a lifting jack embodying a member that is adapted for relative movement with respect to a jack rod, a bit holder pivotally mounted at one end to said member and formed with a square hollow socket in the other end, and a bit which is square in cross section forming four plane side surfaces and which is also of substantially greater length than its cross dimension removably supported within the socket of said holder, said bit formed with transverse surfaces at its opposite longitudinal ends that extend at right angles with each of said plane side surfaces to thereby form a multiplicity of sharp biting surfaces on the opposite ends for engaging the jack rod, to thereby provide substitute biting surfaces by axial rotation of the bit with respect the bit holder, and by end-toend reversal of the bit within the holder.

References Cited in the file of this patent UNITED STATES PATENTS 402,381 Aiken Apr. 30, 1889 2,268,243 Curtis Dec. 30, 1941 2,673,064 Patterson et a1 Mar. 23, 1954 2,673,065 Patterson Mar. 23, 1954 2,673,066 Norman Mar. 23, 1954 2,673,067 Fredrickson Mar. 23, 1954 FOREIGN PATENTS 14,452 Great Britain June 19, 1911 

